1. Field of the Invention
This invention relates to an electrostatic chuck for attracting a semiconductor substrate or a glass substrate, and to a method for manufacturing the same.
2. Background Art
An electrostatic chuck is used as a means for attracting and holding a semiconductor substrate or a glass substrate in a vacuum processing chamber, which is subjected to processing heat of plasma for etching, CVD, sputtering, ion implantation, and ashing (JP-A 10-223742(Kokai) (1998), JP-A 2003-152065(Kokai), JP-A 4-133443(Kokai) (1992), JP-A 2001-338970(Kokai)).
FIG. 4 shows the structure of an electrostatic chuck of a comparative example disclosed in JP-A 10-223742(Kokai). A dielectric layer 103 holding electrodes 102 inside is integrally bonded onto a metal plate 100 via an organic adhesive 101 such as a silicone resin. With regard to the method for embedding the electrode 102 in the dielectric layer 103, the electrode (tungsten) is printed on the surface of a ceramic green sheet, which is to be a dielectric layer by sintering, and another ceramic green sheet is overlaid thereon, and sintered (hot press). JP-A 2003-152065(Kokai) also discloses a configuration of an electrostatic chuck generally identical to the foregoing with the average particle size of the ceramic being held down to 2 μm or less.
The electrostatic chuck of the type shown in FIG. 4 is not convenient to manufacture because the method for embedding the electrode 102 is complicated, prolonging the production time. More specifically, in order to embed the electrode inside the dielectric, two dielectric substrates are sintered and shaped, and then an electrode material is sandwiched therebetween and integrated by hot press processing such as heating and pressurizing. Thus a technically sophisticated and complicated process is needed.
In contrast to the above electrostatic chuck holding electrodes inside the dielectric, which involves a complicated process, electrostatic chucks manufactured by a simplified process are also proposed (JP-A 4-133443(Kokai), JP-A 2001-338970(Kokai)).
JP-A 4-133443(Kokai) discloses an electrostatic chuck in which an electrode formed on the surface of a dielectric substrate is oppositely fixed to a base plate made of an aluminum or other metal material via an adhesive.
JP-A 2001-338970(Kokai) discloses an electrostatic chuck in which an electrode is formed on the surface of a dielectric substrate, which is overlaid with an insulative resin such as polyimide and bonded to a metal base plate.
However, neither of the electrostatic chucks of JP-A 4-133443(Kokai) and JP-A 2001-338970(Kokai) can realize a structure of satisfying sufficient cooling performance while maintaining high insulation reliability.
The insulation reliability of the electrostatic chuck of JP-A 4-133443(Kokai) can indeed be enhanced if the insulative adhesive interposed between the electrode 2 and the base plate 3 is sufficiently thickened. However, silicone and other resins commonly used as an adhesive have poor thermal conductivity. In particular, the performance of cooling a wafer attracted to the surface of the dielectric substrate cannot be sufficiently ensured.
The electrostatic chuck of JP-A 2001-338970(Kokai) is based on an insulative resin such as polyimide, which has poor thermal conductivity. Hence, likewise, the performance of cooling a wafer cannot be sufficiently ensured.